Anthropic · Claude · Fable · Mythos

Claude Sonnet 5.5

Released 28 Sep 2026 · 6 days after Claude Opus 5.5

Intelligence

54.5

#3 of 22 scored releases to that date

Price

$4.00

per 1M tokens, 3:1 in/out · $2 in / $10 out

Speed

135

output tokens/s, median

Weights

Closed

US lab

Anthropic’s best score over time